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-   -   [Other] extrude2DMesh linearNormal not working (https://www.cfd-online.com/Forums/openfoam-meshing/242887-extrude2dmesh-linearnormal-not-working.html)

shamantic May 17, 2022 09:31

extrude2DMesh linearNormal not working
 
Hello,


to create a thin solid layer upon a complex curved surface, I created a MeshedSurface

using the wavefront .obj format. With paraview, I checked that the point-normals are as expected and contained in the .obj file.


Now I see two strange effects with extrude2DMesh:
1. The input surface file must be called MeshedSurface.obj and reside in the project directory. The file specified in the extrude2DMeshDict file is ignored. EDIT: this is not a showstopper;)

2. extrude2DMesh correctly echoes the required thickness to the log, but does not offset any vertices, so all those edges are collapsed immediately. paraFoam counts doubled number of points anyway for one layer added. EDIT: this is a showstopper :(

Anyone have a clue what might go wrong here? Details see below.


EDIT: Did anyone get the extrudeModel linearNormal to work during the last year? Which file format was used with success?



EDIT: I did "successfully" use the linearDirection mode which did offset the points to create volumes.



OpenFoam.com-v1912 on Ubuntu 18.04.06

cmdline: extrude2DMesh MeshedSurface
system/extrude2DMeshDict (relevant portions only):
/*--------------------------------*- C++ -*----------------------------------*\
| ========= | |
| \\ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \\ / O peration | Version: v1912 |
| \\ / A nd | Website: www.openfoam.com |
| \\/ M anipulation | |
\*---------------------------------------------------------------------------*/
FoamFile
{
version 2.0;
format ascii;
class dictionary;
object extrude2DMeshDict;
}
constructFrom surface;
// ....



surface "constant/triSurface/nose_p.obj";
patchType wall;
// Flip surface normals before usage. Valid only for extrude from surface or
// patch.
flipNormals false;

//- Linear extrusion in point-normal direction
extrudeModel linearNormal;


nLayers 1;
expansionRatio 1;


linearNormalCoeffs
{
thickness 0.1;
}
mergeFaces false;

// Merge small edges. Fraction of bounding box.
mergeTol 0;
-------------------------------------------------

The output of extrude2DMesh contains (only relevant portions shown for brevity)



Extruding from MeshedSurface at time 0
Selecting extrudeModel linearNormal
Selected extrudeModel for linearNormal using coeffs
{
thickness 0.1;
}

Flipping face order if necessary.
Calculating neighbours.
Constructing patches.
Adding patch front at index 1 for front faces.

Adding patch back at index 2 for back faces.

Added 76760 points to layer 0
Added 76760 points to layer 1
Merging edge (0 76760) since length 0 << 0.010808
Merging edge (1 76761) since length 0 << 0.010808

.... nearly all edges merged ....
Uncollapsed edges = 76630 / 533326
Uncollapsed edges = 0 / 533326
Number of points : 153520
Not visited : 0
Not collapsed : 153520
Collapsed : 0

Collapsing 0 cells

Writing extruded mesh to time = 0.001

End


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